Improve error handling, introduce lua stack trace processing.

src/main/java/lua/value/LValue.java

@@ -33,7 +33,7 @@ public class LValue {
 	// perform a lua call, return true if the call is to a lua function, false
 	// if it ran to completion.
 	public boolean luaStackCall(VM vm) {
-		luaUnsupportedOperation();
+		vm.lua_error("attempt to call "+this);
 		return false;
 	}